Since I haven't read the essays you're talking about, I cannot comment specifically about the ideas as ideas. Still an essay is an essay and not a story and for me the stories are the heart and the ideas only interesting because they throw light on or deepen one's appreciation of the stories. Do you find that new ideas or conceptions of orcs in these essays in any way resonate with or throw new light on the portrayal of orcs either in The Hobbit or LoTR? Or in The Silmarillion? Is there available any version of a story or part of a story where these different kinds of orcs are being portrayed or mentioned?

Of course it's possible to lead a purely theoretical discussion about how Tolkien actually thought of orcs and their nature. But without a reference to concrete stories or versions of stories, such a discussion quickly can deteriorate into mere speculation about possibilities - it takes place in what I would call a void. What such parts of essays show is how Tolkien grappled with and continued to reconsider fundamental ideas about orcs, but never actually managed to go any further with it in practice. You could never know if these conceptions of orcs would end up as one of those many drafts or thoughts which would be abandonded. What you're actually left with are the stories and versions of stories that Tolkien managed to write.

Christopher Tolkien wrote in the foreword to The Silmarillion that in his latest years Tolkien devoted himself more to theological and philosophical preoccupations of his mythology and his prose and poetry came more in the background. It strikes me that the essays you're talking about in Morgoth's Ring are part of this tendency. Christopher Tolkien also wrote that trying to show The Silmarillion as a continuing evolvement of over half a decade would only lead to confusion and submerge what is essential. The discussion about the development of Tolkien's ideas are only applicable to the understanding of The Silmarillion, since LoTR was never rewritten and the rewriting of The Hobbit was abandonded. With The Silmarillion you have many different versions and concepts for the same stories and there you can argue which versions should be considered to have primacy and which shouldn't. But if the story is to succeed as a story or cycle of stories it still needs a very disciplined approach, where you select versions which are compatible with each other and produce a reasonably coherent and consistent tale.

When you adapt The Hobbit, you adapt a story with its own internal logic and vision, and most of all you adapt a story and not a random collection of fragments and ideas. It's definitely useful to have a knowledge of Tolkien's ideas, but the main basis is the story you're trying to adapt, not speculations and thoughts put forth in essays that are not relevant to the story. By the way I've already accepted and understood that the adaptation of the Hobbit enhances and elaborates the context around the main story, but I still expect that what they actually put on film should lead back to hints, themes and ideas in the original story.